|
Function of Topsoil
Topsoil stores plant nutrients, air, and moisture. It is a virtual factory of intense biological activity; innumerable fungi and bacteria in topsoil greak down organic matter and make the soil richer. Topsoil, therefore, is essential to productive agriculture. The nutrients in topsoil are crucial to crop production. They are the food of plants. So if the topsoil is lost, you cannot get a good harvest from your land unless you use expensive commercial fertilizer. One best thing you can do, therefore, is to protect your hilly land from soil erosion. Bear in mind that poor soil makes a farmer poor and the land poor.
Controlling Erosion
There are several traditional ways of controlling soil erosion, such as reforestation, terracing, multiple cropping, contouring, and cover cropping. The Asian Rural Life Development Foundation (ARLDF) in Kinuskusan, Bansalan, Davao del Sur, Philippines, promotes an erosion control technique that is both easier and less expensive to implement than the traditional methods. This technology is known as SALT or Sloping Agricultural Land Technology.
The SALT System
Salt is a package technology on soil conservation and food production, integrating different soil conservation measures in just one setting. Basically, SALT is a method of growing field and permanent crops in 3-meter to 5-meter-wide bands between contoured rows of nitrogen fixing trees. The nitrogen fixing trees are thickly planted in double rows to make hedgerows. When a hedge is 1.5 to 2 meters tall, it is cut down to about 75 centimeters and the cuttings (tops) are placed in alley-ways to serve as organic fertilizers.
SALT: An Agroforestry Scheme
SALT is a diversified farming system which can be considered agroforestry since rows of permanent shrubs like coffee, cacao, citrus and other fruit trees are dispersed throughout the farm plot. The strips not occupied by permanent crops, however, are planted alternately to cereals (corn, upland rice, sorghum, etc.) or other crops (sweet potato, melon, pineapple, castor bean, etc.) and legumes (soybean, mung bean, peanut, etc.). This cyclical cropping provides the farmer some harvest throughout the year. SALT also includes planting of trees for timber and firewood on surrounding boundaries. Examples of tree species for "boundary forestry" in SALT are mahoganies, casuarinas, sesbanias, cashew nuts, pili nuts, etc.
History of SALT
SALT was developed on a marginal site in Kinuskusan, Bansalan, Davao del Sur by the Mindanao Baptist Rural Life Center (MBRLC). In 1971, MBRLC started to employ contour terraces in its sloping areas. Dialogues with local upland farmers acquainted the Center with farm problems and needs which gave the Center the impetus to work out a relevant and appropriate upland farming system.
From testing different intercropping schemes and observing ipil-ipil-based farming systems in Hawaii and at the Center, the SALT was finally verified and completed in 1978. While it was still in the developing stage, the following guidelines were considered essential. The system must:
- adequately control soil erosion,
- help restore soil structure and fertility,
|
